384 Dr. G. Jonstone Stoney on the 



The term Ampere is here used to designate the B.A. unit 

 of quantity corresponding to the ohm (the B.A. electromag- 

 netic unit of resistance), the volt (the corresponding unit of 

 electromotive force), the weber (unit of current), and the 

 farad (unit of capacity). The electrostatic units of the B.A. 

 series might with great advantage be called the static-ampere, 

 static-ohm, static-volt, and static-farad. 



4. Units like the above, whether of the metric or of the 

 B.A. series, of which three are fundamental, and all others 

 derived from them in such a way as will exclude unnecessary 

 coefficients from our equations, are called systematic units. 

 In forming the existing artificial series of systematic units, it 

 has been usual to regard the units of length, time, and mass 

 as fundamental, and the rest as derived; but there is nothing 

 to prevent our regarding any three independent members of the 

 series as fundamental , and deriving the others from them. It is 

 the aim of the present paper to point out that Nature presents 

 us with three such units ; and that if we take these as our 

 fundamental units instead of choosing them arbitrarily, we 

 shall bring our quantitative expressions into a more conve- 

 nient, and doubtless into a more intimate, relation with Nature 

 as it actually exists. I will then approximate to the values of 

 the units of length, time, and mass belonging to this, which is 

 a truly natural series of physical units. 



5. For such a purpose we must select phenomena that pre- 

 vail throughout the whole of Nature, and are not specially 

 associated with individual bodies. The first of Nature's quan- 

 tities of absolute magnitude to which I will invite attention is 

 that remarkable velocity of an absolute amount, independent 

 of the units in which it is measured, which connects all syste- 

 matic electrostatic units with the electromagnetic units of the 

 same series. I shall call this velocity Vi- If it were taken 

 as our unit velocity, we should at one stroke have an immense 

 simplification introduced into our treatment of the whole range 

 of electric phenomena, and probably into our study of light 

 and heat. 



Again, Nature presents us with one particular coefficient of 

 gravitation, of an absolute amount independent of the units in 

 which it is measured, and which appears to extend to ponder- 

 able matter of every description throughout the whole material 

 universe. This coefficient I shall call Q Y . If we were to take 

 this as our unit of coefficients of attraction, it is presumable 

 that we might thereby lay the foundation for detecting wherein 

 lies the connexion which we cannot but suspect between this 

 most wonderful property common to all ponderable matter 

 and the other phenomena of nature. 



